INTRODUCTION: Predictors of COVID-19 vaccine immunogenicity and the influence of prior SARS-CoV-2 infection require elucidation. METHODS: Stop the Spread Ottawa is a prospective cohort of individuals at-risk for or who have been infected with SARS-CoV-2, initially enrolled for 10 months beginning October 2020. This analysis focuses on safety and immunogenicity of the initial two doses of COVID-19 vaccine. RESULTS: Post-vaccination data with blood specimens were available for 930 participants. 22.8% were SARS-CoV2 infected prior to first vaccine dose. Cohort characteristics include: median age 44 (22, 56), 66.6% female, 89.0% white, 83.2% employed. 38.1% reported two or more comorbidities and 30.8% reported immune compromising condition(s). Over 95% possessed IgG spike and RBD titres 3 months post second vaccine dose. By multivariable analysis, increasing age and high-level immune compromise predicted diminishing IgG spike and RBD titres at month 3 post second dose. IgG spike and RBD titres were higher immediately post vaccination in those with SARS-CoV-2 infection prior to first vaccination and spike titres were higher at 6 months in those with wider time intervals between dose 1 and 2. IgG spike and RBD titres and neutralization were generally similar by sex, weight and whether receiving homogeneous or heterogeneous combinations of vaccines. Common post dose 1 vaccine symptoms included fatigue (64.7%), injection site pain (47.5%), headache (27.2%), fever/chills (26.2%), body aches (25.3%). These symptoms are similar with subsequent doses. CONCLUSION: The initial two COVID-19 vaccine doses are safe, well-tolerated and highly immunogenic across a broad spectrum of vaccine recipients.

Background: Measures introduced during the COVID-19 pandemic intended to address the spread of SARS-CoV-2 may also influence the incidence of other common seasonal respiratory viruses (SRV). This evaluation reports laboratory confirmed cases of common SRV in a well-defined region of central Canada to address this issue. Methods: Surveillance data for common non-SARS-CoV-2 SRV in the Ottawa, Canada region was provided by the Eastern Ontario Regional Laboratory Association (EORLA) reference virology lab. Weekly reports of the number of positive tests and proportion that yielded positive results was analyzed from August 26, 2018 to January 2, 2022. Results: A drastic reduction in influenza and other common SRV was observed during the 2020-2021 influenza season in the Ottawa region. Influenza was virtually undetected post SARS-CoV-2 emergence. Rhinoviruses and enteroviruses were the only viruses that remained relatively unaffected during this period. Conclusions: We speculated that the introduction of non-pharmaceutical measures including masking to prevent SARS-CoV-2 transmission contributed to the near absence of SRV in the Ottawa region. These measures should remain a key component in addressing spikes in SRV activity and future pandemics.